Currently, there is increasing interest in a full-duplex radio system, particularly for a base station of a cellular communications network. As used herein, a full-duplex radio system is a radio system that both transmits and receives using the same time and frequency resources. Thus, for a base station, a full-duplex radio system is a radio system that simultaneously transmits the downlink and receives the uplink using the same frequency resources. The primary challenge in a full-duplex radio system is detecting a weak received signal in the presence of a much stronger transmit signal. Isolation between the received signal and the transmit signal is normally achieved with filtering in a Frequency Division Duplexing (FDD) radio system or by using a half-duplex scheme, such as in a Time Division Duplexing (TDD) radio system. However, neither of these techniques can be applied to provide isolation in a full-duplex radio system.
Thus, there is a need for systems and methods for providing isolation between the received signal and the transmit signal in a full-duplex radio system.